(define pi 3.1415927)

(define (rec-draw-line x1 y1 x2 y2 current-depth max-depth)
  (cond ((< current-depth max-depth)
         (let ((mx1 (+ x1 (* (/ (- x2 x1) 4) 2)))
               (my1 (+ y1 (* (/ (- y2 y1) 4) 2)))
               (mx2 (+ x1 (* (/ (- x2 x1) 4) 3)))
               (my2 (+ y1 (* (/ (- y2 y1) 4) 3))))
           (rec-draw-line  x1  y1 mx1 my1 (1+ current-depth) max-depth)

           (rec-draw-line mx1 (- my1 5)
                          mx2 (- my2 5)
                          (1+ current-depth) max-depth)

           (rec-draw-line mx2 my2  x2  y2 (1+ current-depth) max-depth)))
        (else
           (draw-line (inexact->exact x1) (inexact->exact y1)
                      (inexact->exact x2) (inexact->exact y2)))))

(define (deg2rad angle)
  (* (/ angle 180) pi))

(define (draw-star-helper x1 y1 angle complete-length current-depth max-depth)
  (cond ((< current-depth max-depth)
         (let* ((length (/ complete-length 2))
                (x2 (+ x1 (* (cos (deg2rad angle)) length)))
                (y2 (+ y1 (* (sin (deg2rad angle)) length))))
           (draw-line (inexact->exact x1) (inexact->exact y1)
                      (inexact->exact x2) (inexact->exact y2))
           (draw-star-helper x2 y2
                             (- angle 15)
                             (- complete-length length)
                             (1+ current-depth) 
                             max-depth)
           ))))

(define (draw-star x1 y1 angle length max-depth)
  (draw-star-helper x1 y1 angle length 0 max-depth))

(init-screen 640 480)
(set-fg-color #x000000)
(set-bg-color #xFFFFFF)
(draw-line 0 0 640 480)
(draw-line 640 0 0 480)

(draw-star 20 400 0 500 100)
(rec-draw-line 10 400 630 400 0 3)

(while #t
       (next-event))

;; EOF ;;